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Aluminum air batteries are an enticing alternative to lithium ion ones, offering one of the "highest chemical energy-density storage materials we know of," according to researchers at MIT. But those metal air batteries have a major problem: they can lose 80 percent of their charge in a month, compared to just 5 percent for a lithium ion battery. However, those researchers found that coating the aluminum electrode in oil when its not in use drastically increases the battery's shelf life, losing just 0.02 percent of its charge a month. Unlike previous attempts, the new method takes advantage of aluminum's "underwater oleophobicity," which allows the electrolyte to rapidly displace water from the electrode's surface when the battery is ready for use.
The result is an aluminum-air prototype with a much longer shelf life than that of conventional aluminum-air batteries. The researchers showed that when the battery was repeatedly used and then put on standby for one to two days, the MIT design lasted 24 days, while the conventional design lasted for only three. Even when oil and a pumping system are included in scaled-up primary aluminum-air battery packs, they are still five times lighter and twice as compact as rechargeable lithium-ion battery packs for electric vehicles, the researchers report. Hart explains that aluminum, besides being very inexpensive, is one of the "highest chemical energy-density storage materials we know of" that is, it is able to store and deliver more energy per pound than almost anything else, with only bromines, which are expensive and hazardous, being comparable. He says many experts think aluminum-air batteries may be the only viable replacement for lithium-ion batteries and for gasoline in cars. Aluminum-air batteries have been used as range extenders for electric vehicles to supplement built-in rechargeable batteries, to add many extra miles of driving when the built-in battery runs out. They are also sometimes used as power sources in remote locations or for some underwater vehicles. But while such batteries can be stored for long periods as long as they are unused, as soon as they are turned on for the first time, they start to degrade rapidly.
The result is an aluminum-air prototype with a much longer shelf life than that of conventional aluminum-air batteries. The researchers showed that when the battery was repeatedly used and then put on standby for one to two days, the MIT design lasted 24 days, while the conventional design lasted for only three. Even when oil and a pumping system are included in scaled-up primary aluminum-air battery packs, they are still five times lighter and twice as compact as rechargeable lithium-ion battery packs for electric vehicles, the researchers report. Hart explains that aluminum, besides being very inexpensive, is one of the "highest chemical energy-density storage materials we know of" that is, it is able to store and deliver more energy per pound than almost anything else, with only bromines, which are expensive and hazardous, being comparable. He says many experts think aluminum-air batteries may be the only viable replacement for lithium-ion batteries and for gasoline in cars. Aluminum-air batteries have been used as range extenders for electric vehicles to supplement built-in rechargeable batteries, to add many extra miles of driving when the built-in battery runs out. They are also sometimes used as power sources in remote locations or for some underwater vehicles. But while such batteries can be stored for long periods as long as they are unused, as soon as they are turned on for the first time, they start to degrade rapidly.